1. Field of the Invention
The present invention relates to a technique, in a system including a chamber serving to maintain an environment different from an external environment, for transmitting a signal between the inside and outside of the chamber. Such a chamber may be, for example, a purge chamber filled with an inert gas inside, or a vacuum chamber. Further, the present invention relates to a device manufacturing apparatus and method applied with such a transmission technique.
2. Description of the Related Art
As semiconductor manufacturing apparatuses, there are known a type having a purge chamber filled with an inert gas inside and a type having a vacuum chamber under negative pressure inside. When transmitting a signal between the inside and outside of the chamber in each of those types of semiconductor manufacturing apparatuses, a feedthrough portion is usually provided at a wall of the chamber and the transmission is carried out through it, thereby preventing leakage of the inert gas inside the chamber to the outside or preventing reduction of the degree of vacuum inside the chamber.
To give an example, in a semiconductor manufacturing apparatus described in JP-A H10-50497, a feedthrough portion is provided at a wall of a vacuum chamber for transmitting therethrough an electrical signal of a probe disposed in the vacuum chamber to the outside thereof. To give a further example, there is also known a semiconductor manufacturing apparatus using optical fibers as signal transmission lines wherein a light emitted by a laser disposed outside a vacuum chamber is introduced into the vacuum chamber through an optical fiber so as to be used for a given measurement and a detected measurement light is guided out to the outside of the vacuum chamber through another optical fiber. In recent years, as semiconductor manufacturing apparatuses have been becoming more complicated and increasing in scale, more units have been installed inside a chamber and, therefore, the number of feedthrough portions for connecting between the inside and outside of the chamber has been increasing.
On the other hand, as a communication technique using optical fibers, there is known, for example, a technique of wavelength division multiplex communication that multiplexes lights having different wavelengths by a multiplexer/demultiplexer to carry out two-way communication through one optical cable (e.g., see JP-A H06-265746).
In general, the chambers of those semiconductor manufacturing apparatuses are required to be very strong in structure because if it is a purge chamber that is filled with an inert gas inside, it should prevent leakage of the purge gas, while, if it is a vacuum chamber, it should ensure a vacuum inside. Therefore, a very large area in the partition wall of the chamber is required only for transmitting one signal through the feedthrough portion. Under these circumstances, there is a problem that if the number of transmission signals is increased, feedthrough portions are required at the wall of the chamber as many as the number of the signals, thereby causing an increase in size and price of the apparatus.
Further, there is also a problem that the degree of inert gas purity or vacuum inside the chamber is lowered due to the influence of outgas discharged from a feedthrough connector so that impurities are mixed into a semiconductor to be manufactured, thereby reducing the yield of semiconductor elements.